Optical sensor systems may include source modules and detection modules to detect the presence of objects there between. The source modules may include a source window member to emit a detection signal such as an infrared signal there through to be received by a detection module through a detection window member thereof. The objects such as volatile organic compounds (VOC) may be detected present in a path of the detection signal. Such optical sensor systems may be included in image forming apparatuses, air quality monitoring devices, or the like.